Field of the Invention
Embodiments of the invention generally relate to an implantable electrical line having an elongate electrical lead.
Description of the Related Art
Generally, implantable electrical lines are used for example as electrode lines (also referred to as “electrodes”) for cardiac pacemakers or defibrillators and are used to transmit electrical pulses from a cardiac pacemaker or defibrillator to electrode poles at or in the vicinity of a distal end of the electrode line. Also, typically, the implantable electrical lines are used conversely to transmit electrical signals from one or more electrode poles to the cardiac pacemaker or defibrillator. To this end, an electrode line typically has one or more electrical conductors, which form one or more leads. Generally, in implantable electrical lines, such as electrode lines, a coil which is formed by one or more electrical conductors wound helically is preferably used as a lead since on the one hand it provides an inner lumen for a guide wire and on the other hand a wound wire is much more stable with respect to permanent bending stress.
Typically, a coil as a lead has one or more disadvantages, which need to be overcome.
For example, generally, implantable heart electrodes such as electrode lines for cardiac pacemakers or defibrillators are subjected to different mechanical stresses. In the case of implantation and explantation of electrode lines, typically, high tensile forces may occur. If the electrode line is arranged in an unfavorable position, generally, radial pressures can be produced, for example between the collarbone and the first rib. A conventional coil is generally not able to cope with such forces. In the case of tensile forces, typically, the coil composite contracts, and in the case of radial pressures the coil composite is disturbed and the coil is at risk of breaking
The coil on the one hand, for example in embodiments of the invention as discussed herein below, may be soft and flexible to not provoke any reactions in the heart and on the other hand may be stable with respect to torsion such that the electrode line may be screwed in.
In addition, generally, elongate electrical lines have the disadvantage that a contained electrical conductor can heat up in an MRI scanner because the alternating magnetic fields prevailing in the MRI scanner induce electrical currents in the electrical conductor that are not insignificant. Therefore, typically, cardiac pacemaker patients cannot generally be examined in a magnetic resonance imaging (MRI) scanner or can only be examined in this way to a limited extent.
Specifically, at least one stimulation electrode line is typically connected to implantable cardiac pacemakers or defibrillators. Generally a stimulation electrode line at its proximal end is intended to be connected to a cardiac pacemaker or defibrillator and therefore has a standardized electrical terminal, and, at its distal end intended for placement in the heart, has one or more electrode poles. Such an electrode pole, generally, is used to deliver electrical pulses to the tissue (myocardium) of the heart or to sense electrical fields in order to sense cardiac activity, also known as sensing. For this purpose, electrode poles typically form electrically conductive surface portions of an electrode line. Electrode poles are typically provided as ring electrodes in the form of a ring around the electrode line or in the form of a point electrode or tip electrode at the distal end of the electrode line. The electrode poles are generally electrically conductively connected via one or more electrical conductors to contacts of the electrical terminal of the electrode line at the proximal end thereof. One or more electrical conductors, which typically electrically connect one or more of the electrode poles to one or more of the contacts, thus generally run between the contacts of the electrical terminal of the electrode lines at the proximal end thereof and the electrode poles at the distal end of the electrode line. These electrical conductors, generally, can be used on the one hand for transmission of stimulation pulses to the electrode poles and on the other hand for transmission of electrical signals, received by means of the electrode poles, to the proximal end of the electrode line, also referred to herein as a function line. Such function lines are generally electrical conductors necessary for the functions of the respective electrode line and as such are exposed to the risk that electrical currents will be induced therein as a result of external alternating magnetic fields. Typically, the currents for example may lead to an undesirable heating of the function lines or of the electrode poles connected thereto or may lead to the delivery of corresponding currents via the electrode poles to surrounding tissue and therefore to a heating of the surrounding tissue.
In order to make an electrode line less sensitive for MRI energies, generally, it is expedient to equip the coil with a high inductance. This is typically achieved with as many windings as possible, which would in turn make the coil mechanically unstable.
Generally, the mechanical disadvantages of a coil are compensated for by external protection in the case of known electrode lines. Outer tubes that are as stable as possible are typically used for electrical insulation and for mechanical protection. Generally, braided tubes are often used in the catheter field in order to make the catheter stable with respect to kinks and torsion. In the electrode field, typically, such concepts have not been previously used. Electrodes of which the coils have been replaced by cables, generally, do not have a lumen for the guide wire and are implanted using special catheters.
Otherwise, typically, the coil geometries would have to be held in the geometric dimensions that are stable when in use.
For example, a disadvantage of typical coils as leads is wherein a coil that has to be mechanically protected by its insulation generally limits the design possibilities of a product.
Another disadvantage of typical coils as leads is wherein a coil that includes conflicting mechanical or electrical properties is typically always a compromise in both directions, which leads to properties of the product in need of improvement. For example, as another disadvantage, a braided tube, of which the insulation is increased, is generally relatively stiff and cannot improve the torsion properties of the coil itself
Generally, additional components in a typical electrode that are intended to improve the magnetic resonance (MR) properties always have mechanical disadvantages. Therefore, a typical electrode including such additional components may thus be more rigid or thicker. In addition the fatigue strength of the electrode may then be impaired in particular when electrically effective components are integrated in the therapeutic circuit in series connection.
In order to make an electrode insensitive with respect to the high-frequency energies from magnetic resonance tomography (MRT), there is a need for additional components, such as inductive filters, band-stop filters or additional energy diverters.